Gardening Articles: Flowers :: Perennials

Thomas Ogren

by Cathy Cromell

Tom Ogren

Before Thomas Ogren wrote Allergy-Free Gardening: The Revolutionary Guide to Healthy Landscaping, he wasn't particularly sympathetic to those who suffer from allergies, including his wife and other family members. "I had read that allergies were psychosomatic, so I believed that," he states. That erroneous belief started changing 20 years ago while Ogren was teaching horticulture to prison inmates in California. "I asked a big, muscle-bound gang member to pull Pride of Madeira weeds," he remembers. The inmate wanted a different job because he had gotten a terrible rash the last time he pulled the weeds. Ogren rubbed some of the prickly leaves on his own arm. "It flamed up, so I gave the inmate another job."

Ogren Plant-Allergy Scale

The next week Ogren drove to the Bay Area from his home in San Luis Obispo, on freeways lined with acacia in full bloom. "I had always liked the monoculture look of mass plantings, but when I arrived in Berkeley, everyone was sneezing except me," he describes.

These back-to-back experiences gave him the idea to do "sniff" tests with his class to determine if certain plants created problems. "We went outside and sniffed everything," he explains, "and a third of the class started sneezing uncontrollably from bottlebrush." Intrigued, he continued the sniff tests for a year with anyone who would volunteer, learning which plants typically triggered reactions. He stopped when a few people became ill.

"I felt so bad about the lack of empathy I had shown my wife that I replaced all the plants in our yard that seemed to cause problems." There was significant improvement in her allergies. Ogren's brother-in-law also replanted his yard. "For the first time in his adult life, he wasn't taking antihistamines," recalls Ogren. Fascinated by these results, Ogren talked to botanists, horticulture professors, and allergists, but there was little data available on plant allergies. His research led him to develop OPALS (Ogren Plant-Allergy Scale) to categorize plants numerically from 1 to 10. The higher the number, the more likely that the plant will cause allergy symptoms. Writing a book was the next step. "I ended up writing the book that I had wanted to buy," he states. "I received 326 book rejections over a 12-year period, but I kept working on it because the topic fascinated me."